The present invention relates to a pneumatic tire, more particularly to a tread profile for a pneumatic tire installed on a vehicle with negative camber capable of improving the aquaplane resistance and uneven wear resistance of the tire.
Heretofore, in order to improve the steering stability and uneven wear resistance of a pneumatic tire, the tread of the tire is provided with a profile such that, in the meridian section of the tire, the radius of curvature is gradually decreased from the tire equator toward the tread edges. Accordingly, the radii of curvature of the treads of land portions (ground contacting portions or elements) formed in the tread of the tire are gradually decreased from the tire equator toward the axial outside.
In such tire, however, the ground pressure of each land portion becomes small in its axial central region when compared with the axial edge regions. As a result, water existing between the axial central region of the land portion and the road surface can not be readily removed.
Japanese Patent Application Publication No. 2005-319890 discloses a pneumatic tire in which the profile of the tread of a center land portion disposed on the tire equator protrudes convexly, radially outwardly from a virtual profile defined by smoothly connecting axial ends of land portions excepting the center land portion (virtual profile corresponding to the above-mentioned conventional profile), and the maximally protruding point is positioned at the axial center of the land portion. In this case, the ground pressure of the center land portion becomes increased in its axial central region, therefore, it is possible to even the ground pressure of the center land portion in the axial direction.
In recent years, on the other hand, there is a trend such that, in order to improve the high speed stability, a pneumatic tire is installed on a passenger car with negative camber.
FIG. 6 shows a ground contact pressure distribution of a pneumatic tire having five straight ribs, to which the tread profile of the above-mentioned prior art is applied, is installed with negative camber. In the figure, the darker the halftone, the higher the ground pressure.
As shown in FIG.6, even in the above-mentioned pneumatic tire, the ground pressure of each land portion becomes higher in the inboard side than in the outboard side, and therefore, the drainage and the uneven wear resistance cannot be improved.